BQ40Z50: Deactivation of Safety PTC Thermistor (PTC to VSS)

Joseph DeWitt

Part Number: BQ40Z50

Hi,

I hope you are doing well.

In order to deactivate the Safety PTC Thermistor, the BQ40Z50 battery pack manager datasheet states "to deactivate this feature connect a 10K Ohm resistor between PTC and VSS." In my schematic I have done so (please see image below) but I am unclear as to what needs to be done to PTCEN. Can this pin simply be connected to VSS as well? Does PTCEN still need to be connected to BAT? Any guidance you can provide would be appreciated. For my application VSS is connected to ground which is why I'm showing the connection to GND.

Best regards,

Joe DeWitt

over 1 year ago

0 Adrian over 1 year ago

TI__Mastermind 37761 points

Hello Joseph,

If this function is not used then PTC should be connected with a 10K resistor in series to BAT and PTCEN connected to Vss.

Sincerely,
Nick Richards

0 Joseph DeWitt over 1 year ago in reply to Adrian

Intellectual 320 points

Hi Nick,

Thanks so much for the feedback. With the configuration you've outline above, if I replace the 10K Ohm resistor with the 10 K PTC thermistor, will the safety PTC thermistor be enabled? The configuration in the datasheet appears to be different so I just wanted to confirm the required configurations for disabling (provided in your previous email) versus enabling (illustration from the datasheet provided below). In the datasheet PTCEN also appears to be connected to BAT.

Thanks in advance for your feedback regarding the correct configurations for disabling versus enabling the PTC thermistor functionality.

Best regards,

Joe DeWitt

0 Adrian over 1 year ago in reply to Joseph DeWitt

TI__Mastermind 37761 points

Hello Joseph,

No, if you do that the PTC will not behave properly. I would recommend following the circuit in the illustration.

Sincerely,
Nick Richards

0 Joseph DeWitt over 1 year ago in reply to Adrian

Intellectual 320 points

Hi Nick,

Was there an attachment or illustration you were intending to include?

Best regards,

Joe DeWitt

0 Adrian over 1 year ago in reply to Joseph DeWitt

TI__Mastermind 37761 points

Hello Joseph,

I was referring to the schematic of the EVM that you included in your previous post.

Sincerely,
Nick Richards

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BQ40Z50: Deactivation of Safety PTC Thermistor (PTC to VSS)